This content originally appeared on CSS-Tricks and was authored by Geoff Graham
Super cool new CodePen feature alert! You’ve probably seen a bunch of “interactive” demos that let you changed values on the fly from a UI panel embedded directly in the demo. Jhey’s demos come immediately to mind, like this one:
That’s a tool called TweakPane doing the work. There’s another one called Knobs by Yair Even Or that Adam Argyle often uses:
I’ve often faked it with either the Checkbox Hack or a sprinkle of JavaScript when I’m demoing a very specific concept:
OK, enough examples because CodePen has a homegrown tool of its own called slideVars. All you have to do is import it and call it in the JavaScript panel:
import { slideVars } from "@codepen/slidevars";
slideVars.init();You can import it into a project off CodePen if you’re so inclined.
That two-liner does a lot of lifting. It auto-detects CSS variables in your CSS and builds the panel for you, absolutely-positioned in the top-right corner:
It looks like you have to declare your variables on the :root element with default usage. I tried scoping them directly to the element and it was a no-go. It’s possible with a manual configuration, though.
Pretty cool, right? You can manually configure the input type, a value range, a default value, unit type, and yes, a scope that targets the element where the variables are defined. As far as units go, it supports all kinds of CSS numeric units. That includes unit-less values, though the documentation doesn’t explicitly say it. Just leave the unit property as an empty string ("").
I guess the only thing I’d like is to tell slideVars exactly what increments to use when manually configuring things. For example, unit-less values simply increment in integers, even if you define the default value as a decimal:
It works in default mode, however:
There’s a way to place the slideVars wherever you want by slapping a custom element where you want it in the HTML. It’s auto-placed at the bottom of the HTML <body> by default.
<slide-vars>
<p>Custom Label!</p>
</slide-vars>Or CSS it by selecting the custom element:
So much fun!
Playing With CodePen slideVars originally published on CSS-Tricks, which is part of the DigitalOcean family. You should get the newsletter.
This content originally appeared on CSS-Tricks and was authored by Geoff Graham
Geoff Graham | Sciencx (2026-01-14T14:59:07+00:00) Playing With CodePen slideVars. Retrieved from https://www.scien.cx/2026/01/14/playing-with-codepen-slidevars/
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